Field of the Invention
The present invention relates to an addition-curable organopolysiloxane resin composition containing a particular barium compound; a cured product of such composition; and a semiconductor device having such cured product.
Background Art
As an LED encapsulation material, those also exhibiting a superior heat resistance, light resistance, workability, adhesion, gas barrier property and curing property are demanded. Conventionally, there have been often used epoxy resins; and thermoplastic resins such as poly (meth)acrylate and polycarbonate. However, as LED light-emitting devices of recent years have shown higher outputs, it is now clear that there exists a problem that heat resistance and discoloration resistance will be impaired if using these thermoplastic resins under a high-temperature environment for a long period of time.
Further, a lead-free solder has been used more often in recent days to solder an optical element(s) to a substrate. Since such lead-free solder has a melting point higher than that of a conventional solder, soldering has to be performed at a temperature of not lower than 260° C. if using the same. However, as a result of performing soldering at such temperature, there will occur problems such as deformation if using the conventional thermoplastic resins as encapsulation materials; or yellowing of such encapsulation material itself due to a high temperature.
In this way, an encapsulation material is now required to exhibit a heat resistance more excellent than ever in consideration of the higher outputs of the LED light-emitting devices and the usage of the lead-free solder. Although there have been proposed, for example, optical resin compositions each obtained by filling a thermoplastic resin with a nano silica for the purpose of improving heat resistance (JP-A-2012-214554 and JP-A-2013-204029), a sufficient heat resistance has not been able to be achieved due to the limitation in the heat resistance of a thermoplastic resin.
Meanwhile, silicone resins as heat-curable resins have been considered as LED encapsulation materials, since they are superior in heat resistance, light resistance and light transmissibility (JP-A-2006-213789, JP-A-2007-131694 and JP-A-2011-252175). However, as LEDs have shown higher outputs, even a silicone resin superior in heat resistance and light resistance will undergo resin oxidation and coloring, and exhibit cracks due to an increase in hardness, when exposed to a temperature greater than 200° C.
As a countermeasure to these problems, there has been considered the usage of a heat stabilizer in a heat-curable silicone resin. Cerium oxide and/or a cerium carboxylate are, for example, used as such heat stabilizer; and it has been confirmed that they bring about an effect of maintaining an initial transmissibility, and an effect of restricting a change in hardness, for example (WO2008/082001 and WO2013/084699). However, there have been observed a significant decrease in the initial transmissibility due to coloring by a heat stabilizer, and a decrease in the luminance of an LED device when such heat stabilizer is used as an encapsulation material for LED device. Therefore, it is required that there be developed an encapsulation material that is not only superior in heat resistance, but also has a high initial transmissibility, and does not cause a light loss in an optical semiconductor device.